About the waveform at the start of LTC4413

Hi Naohisa,
What kind of load do you have on OUTA/B?

On page 8 in the datasheet:
"The LTC4413-1 (or LTC4413-2) is recommended for
applications with demanding load step or fast slew rate
requirements. The LTC4413-1 and LTC4413-2 provide better
load regulation in these environments at the expense
of higher quiescent current. The LTC4413 is optimized
for lower power consumption and should not be used in
high slew rate environments or when large and fast load
transients are anticipated."

The -1 or -2 version may resolve your issue.

-Aaron

Hi Aaron,

thank you for your answer.

Nothing is connected to OUTA.
SATA-connected SSD (before booting), SD card (before booting), Buffer-IC, and several logic ICs are connected to OUTB.

By the way, there is no change in the waveform even if SSD and SD card are not connected (load is only a few logic ICs).

After all, is the slew rate too high?

For LTC4413 not of -1, -2
Is this phenomenon at startup normal?

Do you know the range of error (time and voltage) in that case?

Because I don't have time to change the design
There is no choice but to use LTC4413.

Best Regards,

Naohisa

naohisa said:

Is this phenomenon at startup normal?

I used the LTC4413 demoboard (DC839A), and applied the same 3.3V input with a 50V/ms slew rate. No load.

OUT waveform looks similar to what you saw.

Here is the same scopeshot, but with the -2 version:

Once IN reaches 3.3V, OUT came up 50us quicker for the -2 version.

naohisa said:

Do you know the range of error (time and voltage) in that case?

I don't see that spec in the datasheet. Sorry.

naohisa said:

Because I don't have time to change the design
There is no choice but to use LTC4413

The -1 and -2 version should have the same pinout, so minimal changes.

-Aaron